a. Field of the Invention
The present invention relates to a method and device for ophthalmoscopy and, more particularly, to a method and device for observing and examining the fundus oculi of human eyes.
B. Description of the Prior Art
Out of known methods for observing the fundus oculi of human eyes, a positive lens is arranged at a position near the eyeball to be observed in one method and observation is made through said positive lens. In another known method, a contact lens is used so that the light will not be refracted by the surface of the cornea of the eyeball to be observed. Out of the above, the method to arrange the positive lens at a position near the eyeball to be observed and to observe through the positive lens has disadvantages that the observer should be skilled and experienced in this method and that the image obtained for observation is an inverted image. The disadvantage of this method that the image is inverted may be eliminated when the observer observes by letting his eyes closely approach said positive lens. In that case, however, the examinee will feel much oppressed because the observer closely approaches the examinee. Besides, the disadvantage that the observer should be skilled and experienced in this observing method cannot be still eliminated. Moreover, in this observing method, the fundus is illuminated through said positive lens. At that time, the illuminating light is reflected by the surface of the cornea and observation is disturbed by the reflected light.
The observing method to use the contact lens has various advantages. That is, in this method, observation is comparatively easy and, moreover, it is possible to observe an erect image. Besides, in this method, it is also possible to illuminate the fundus by means of optical fiber bundles arranged along the circumference of the contact lens. Therefore, comparatively favourable illumination can be attained. Moreover, when a large number of optical fiber bundles are arranged along the circumference of the contact lens, it is possible to illuminate a wide area of the fundus. The method to use the contact lens, however, has a disadvantage that the image to be observed cannot be magnified.